This invention relates to an apparatus and to a method for pelletizing materials.
Various apparatus for pelletizing particulate materials are known. In U.S. Pat. Nos. 3,781,151 and 4,017,241, agglomerating novel feeding devices for producing charcoal briquettes by feeding such particulate material between a pair of compacting rolls having a plurality of circumferentiallyspaced formation pockets for peripherially forming such briquette composite structures. Although such a peripheral compaction process can be employed for converting particulate material to its agglomerated form using the above compaction apparatus, it cannot be readily used on material which has not been previously particularized, and in many cases without the introduction of binder agents for adhering the particulate material. Another apparatus is described in U.S. Pat. No. 4,022,562 for pelletizing material, which has been previously particularized, to form cattle feed and the like. In this case the starting material is introduced into the interior of an annular die, commonly known as a California pellet mill. The pelletizable material requires particularization prior to such introduction. This results in costly additional processing steps prior to pelletizing and eliminates substantial fiber length and fiber identity. The feed material, in any case, is then milled into a pulverized form using fixed internally mounted pressure rollers which crush the material as the annular die is rotated thereabout. This pulverized material is then extruded through bores in the annular die housing. In commercial use, adhesive binders are typically added to the pulverized material if pellets of any substantial size are to be produced which are capable of retaining their structural integrity. In U.S. Pat. No. 3,962,462, particularized ingredients in the form of a semi-moist dough-like material is extruded through a die onto a conveyor and then dried in an oven.
In many uses there is a need for high fiber length pellets. An example of such a situation is when animal feed pellets are formed from fibers such as straw and alfalfa, particularly coarse fibers, instead of particularized materials. These materials can be more readily digested in long fiber pellet form, resulting in the formation of more nutrients in the animal's stomach. However, pellets of any substantial fiber length size cannot be directly made by known pelletizing methods. There are also materials which are not directly conventionally pelletizable at ambient conditions, such as whole wood fibers, cellulosic papermaking fibers, and even polymeric materials such as plastics and the like.
Therefore, a need exists for a system which will directly pelletize coarse fibers, long fiber materials, and even particularized fibers and materials, which is not costly and time consuming to operate, and which will directly produce a highly fibrous end product for animal use and the like. Additionally, a further need exists for a system which will directly pelletize materials such as wood and cellulosic fibers, polymers, and the like.